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Supermassive Black Hole (supermassive + black_hole)
Selected AbstractsSurprising evolution of the parsec-scale Faraday Rotation gradients in the jet of the BL Lac object B1803+784MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2009M. Mahmud ABSTRACT Several multifrequency polarization studies have shown the presence of systematic Faraday Rotation gradients across the parsec-scale jets of active galactic nuclei, taken to be due to the systematic variation of the line-of-sight component of a helical magnetic (B) field across the jet. Other studies have confirmed the presence and sense of these gradients in several sources, thus providing evidence that these gradients persist over time and over large distances from the core. However, we find surprising new evidence for a reversal in the direction of the Faraday Rotation gradient across the jet of B1803+784, for which multifrequency polarization observations are available at four epochs. At our three epochs and the epoch of Zavala & Taylor, we observe transverse rotation measure (RM) gradients across the jet, consistent with the presence of a helical magnetic field wrapped around the jet. However, we also observe a ,flip' in the direction of the gradient between 2000 June and 2002 August. Although the origins of this phenomenon are not entirely clear, possibly explanations include (i) the sense of rotation of the central supermassive black hole and accretion disc has remained the same, but the dominant magnetic pole facing the Earth has changed from north to south, (ii) a change in the direction of the azimuthal B field component as a result of torsional oscillations of the jet and (iii) a change in the relative contributions to the observed RMs of the ,inner' and ,outer' helical fields in a magnetic-tower model. Although we cannot entirely rule out the possibility that the observed changes in the RM distribution are associated instead with changes in the thermal-electron distribution in the vicinity of the jet, we argue that this explanation is unlikely. [source] Deep spectroscopy of 9C J1503+4528: a very young compact steep spectrum radio source at z= 0.521MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2006K. J. Inskip ABSTRACT 9C J1503+4528 is a very young compact steep spectrum radio galaxy, with an age of the order of 104 yr. This source is therefore an ideal laboratory for the study of the intrinsic host galaxy/intergalactic medium properties, interactions between the radio source and surrounding interstellar medium, links between star formation and active galactic nucleus (AGN) activity and the radio source triggering mechanism. Here we present the results of a spectroscopic analysis of this source, considering each of these aspects of radio source physics. We find that shock ionization by the young radio source is important in the central regions of the galaxy on scales similar to that of the radio source itself, whilst evidence for an AGN ionization cone is observed at greater distances. Line and continuum features require the presence of a young stellar population (YSP), the best-fitting model for which implies an age of 5 × 106 yr, significantly older than the radio source. Most interestingly, the relative sizes of radio source and extended emission-line region suggest that both AGN and radio source are triggered at approximately the same time. If both the triggering of the radio source activity and the formation of the YSP had the same underlying cause, this source provides a sequence for the events surrounding the triggering process. We propose that the AGN activity in 9C J1503+4528 was caused by a relatively minor interaction, and that a supermassive black hole powering the radio jets must have been in place before the AGN was triggered. [source] Supermassive black hole mass functions at intermediate redshifts from spheroid and AGN luminosity functionsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2006Naoyuki Tamura ABSTRACT Redshift evolution of supermassive black hole mass functions (BHMFs) is investigated up to z, 1. BHMFs at intermediate redshifts are calculated in two ways. One way is from early-type galaxy luminosity functions (LFs); we assume an MBH,Lsph correlation at a redshift by considering a passive evolution of Lsph in the local relationship. The resultant BHMFs (spheroid-BHMFs) from LFs of red-sequence galaxies indicate a slight decrease of number density with increasing redshift at MBH, 107.5,8 M,. Since a redshift evolution in slope and zeropoint of the MBH,Lsph relation is unlikely to be capable of making such an evolution in BHMF, the evolution of the spheroid-BHMFs is perhaps due mainly to the decreasing normalization in the galaxy LFs. We also derive BHMFs from LFs of morphologically selected early-type galaxies. The resultant BHMFs are similar to those from the red-sequence galaxies, but show a small discrepancy at z, 1 corresponding to an increase of supermassive black hole (SMBH) number density by ,0.3 dex. We also investigate how spheroid-BHMFs are affected by uncertainties existing in the derivation in detail. The other way of deriving a BHMF is based on the continuity equation for number density of SMBHs and LFs of active galactic nucleus (AGN). The resultant BHMFs (AGN-BHMFs) show no clear evolution out to z= 1 at MBH, 108 M,, but exhibit a significant decrease with redshift in the lower mass range. Interestingly, these AGN-BHMFs are quite different in the range of MBH, 108 M, from those derived by Merloni (2004), where the fundamental plane of black hole activity is exploited. Comparison of the spheroid-BHMFs with the AGN-BHMFs suggests that at MBH, 108 M,, the spheroid-BHMFs are broadly consistent with the AGN-BHMFs out to z, 1. Although the decrease of SMBH number density with redshift suggested by the spheroid-BHMFs is slightly faster than that suggested by the AGN-BHMFs, we presume this to be due at least partly to a selection effect on the LFs of red-sequence galaxies; the colour selection could miss spheroids with blue colours. The agreement between the spheroid-BHMFs and the AGN-BHMFs appears to support that most of the SMBHs are already hosted by massive spheroids at z, 1 and they evolve without significant mass growth since then. [source] Infrared mergers and infrared quasi-stellar objects with galactic winds , III.MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2005Mrk 231: an exploding young quasi-stellar object with composite outflow/broad absorption lines (and multiple expanding superbubbles) ABSTRACT We present a study of outflow (OF) and broad absorption line (BAL) systems in Mrk 231, and in similar infrared (IR) quasi-stellar objects (QSOs). This study is based mainly on one-dimensional and two-dimensional spectroscopy (obtained at La Palma/William Herschel Telescope, Hubble Space Telescope, International Ultraviolet Explorer, European Southern Observatory/New Technology Telescope, Kitt Peak National Observatory, Apache Point Observatory and Complejo Astronomico El Leoncito observatories) plus Hubble Space Telescope images. For Mrk 231, we report evidence that the extreme nuclear OF process has at least three main components on different scales, which are probably associated with: (i) the radio jet, at parsec scale; (ii) the extreme starburst at parsec and kiloparsec scale. This OF has generated at least four concentric expanding superbubbles and the BAL systems. Specifically, inside and very close to the nucleus the two-dimensional spectra show the presence of an OF emission bump in the blend H,+[N ii], with a peak at the same velocity of the main BAL-I system (VEjection BAL-I,,4700 km s,1). This bump was more clearly detected in the area located at 0.6,1.5 arcsec (490,1220 pc), to the south-west of the nucleus core, showing a strong and broad peak. In addition, in the same direction [at position angle (PA) ,,120°, i.e. close to the PA of the small-scale radio jet] at 1.7,2.5 arcsec, we also detected multiple narrow emission-line components, with ,greatly' enhanced [N ii]/H, ratio (very similar to the spectra of jets bow shocks). These results suggest that the BAL-I system is generated in OF clouds associated with the parsec-scale jet. The Hubble Space Telescope images show four (or possibly five) nuclear superbubbles or shells with radii r, 2.9, 1.5, 1.0, 0.6 and 0.2 kpc. For these bubbles, the two-dimensional H, velocity field map and two-dimensional spectra show the following. (i) At the border of the more extended bubble (S1), a clear expansion of the shell with blueshifted velocities (with circular shape and at a radius r, 5.0 arcsec). This bubble shows a rupture arc , to the south , suggesting that the bubble is in the blowout phase. The axis of this rupture or ejection (at PA , 00°) is coincident with the axis of the intermediate and large-scale structures detected at radio wavelengths. (ii) In addition, in the three more external bubbles (S1, S2, S3), the two-dimensional William Herschel Telescope spectra show multiple emission-line components with OF velocities, of ,VOF Bubble, S1, S2 and S3 =[,(650 , 420) ± 30], [,500 ± 30] and [,230 ± 30] km s,1. (iii) In the whole circumnuclear region (1.8 < r < 5 arcsec), the [N ii]/H, and [S ii]/H, narrow emission-line ratios show high values (>0.8), which are consistent with low-ionization nuclear emission-line region/OF processes associated with fast velocity shocks. Therefore, we suggest that these giant bubbles are associated with the large-scale nuclear OF component, which is generated , at least in part , by the extreme nuclear starburst: giant supernova/hypernova explosions. The variability of the short-lived BAL-III Na i D system was studied, covering almost all the period in which this system appeared (between ,1984 and 2004). We have found that the BAL-III light curve is clearly asymmetric with a steep increase, a clear maximum and an exponential fall (similar to the shape of a supernova light curve). The origin of this BAL-III system is discussed, mainly in the framework of an extreme explosive event, probably associated with giant supernova/hypernova explosions. Finally, the IR colour diagram and the ultraviolet BAL systems of IR + GW/OF + Fe ii QSOs are analysed. This study shows two new BAL IR QSOs and suggests/confirms that these objects could be nearby young BAL QSOs, similar to those detected recently at z, 6.0. We propose that the phase of young QSOs is associated with accretion of a large amount of gas (by the supermassive black hole) + extreme starbursts + extreme composite OFs/BALs. [source] The XMM,Newton Needles in the Haystack Survey: the local X-ray luminosity function of ,normal' galaxiesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2005I. Georgantopoulos ABSTRACT In this paper we estimate the local (z < 0.22) X-ray luminosity function of ,normal' galaxies derived from the XMM,Newton Needles in the Haystack Survey. This is an on-going project that aims to identify X-ray-selected normal galaxies (i.e. non-AGN dominated) in the local Universe. We are using a total of 70 XMM,Newton fields covering an area of 11 deg2 which overlap with the Sloan Digital Sky Survey Data Release 2. Normal galaxies are selected on the basis of their resolved optical light profile, their low X-ray-to-optical flux ratio [log (fx/fo) < , 2] and soft X-ray colours. We find a total of 28 candidate normal galaxies to the 0.5,8 keV band flux limit of ,2 × 10,15 erg cm,2 s,1. Optical spectra are available for most sources in our sample (82 per cent). These provide additional evidence that our sources are bona fide normal galaxies with X-ray emission coming from diffuse hot gas emission and/or X-ray binaries rather than a supermassive black hole. 16 of our galaxies have narrow emission lines or a late-type spectral energy distribution (SED) while the remaining 12 present only absorption lines or an early-type SED. Combining our XMM,Newton sample with 18 local (z < 0.22) galaxies from the Chandra Deep Field North and South surveys, we construct the local X-ray luminosity function of normal galaxies. This can be represented with a Schechter form with a break at L,, 3+1.4,1.0× 1041 erg s,1 and a slope of ,, 1.78 ± 0.12. Using this luminosity function and assuming pure luminosity evolution of the form ,(1 +z)3.3 we estimate a contribution to the X-ray background from normal galaxies of ,10,20 per cent (0.5,8 keV). Finally, we derive, for the first time, the luminosity functions for early- and late-type systems separately. [source] Discovery of an unusual new radio source in the star-forming galaxy M82: faint supernova, supermassive black hole or an extragalactic microquasar?MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY: LETTERS (ELECTRONIC), Issue 1 2010T. W. B. Muxlow ABSTRACT A faint new radio source has been detected in the nuclear region of the starburst galaxy M82 using Multi-Element Radio-Linked Interferometer Network radio observations designed to monitor the flux density evolution of the recent bright supernova SN 2008iz. This new source was initially identified in observations made between 2009 May 1 and 5 but had not been present in observations made 1 week earlier, or in any previous observations of M82. In this Letter, we report the discovery of this new source and monitoring of its evolution over its first 9 months of existence. The true nature of this new source remains unclear, and we discuss whether this source is an unusual and faint supernova, a supermassive black hole associated with the nucleus of M82 or intriguingly the first detection of radio emission from an extragalactic microquasar. [source] Isothermal shocks in Abell 2199 and 2A 0335+096?MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY: LETTERS (ELECTRONIC), Issue 1 2006J. S. Sanders ABSTRACT We report on a partially circular X-ray surface brightness discontinuity found at about 55 kpc from the centre of Abell 2199 with Chandra X-ray Observatory observations. Unlike cold fronts found in other clusters, the feature shows no significant temperature change across it but has an apparent density jump. We therefore identify it as a weak isothermal shock associated with the central active galactic nucleus and the inflation of its radio bubbles, as found in the Perseus cluster. We examine a similar feature at 40 kpc radius found by Mazzotta et al. in 2A 0335+096, and conclude that it too may be an isothermal shock. The change in density if these are shocks implies a Mach number of ,1.5. If the isothermal nature of these features is confirmed by deeper observations, the implication is that such shocks are common in clusters of galaxies, and are an important mechanism for the transport of energy from a central supermassive black hole into the cluster core. [source] Black hole leaves home after confrontationASTRONOMY & GEOPHYSICS, Issue 3 2010Article first published online: 24 MAY 2010 An undergraduate astronomer has found a supermassive black hole apparently heading out of its home galaxy at speed, in what researchers suggest is the aftermath of a black hole merger. If so, there may be many more such objects to be found, casting light on the mechanics of black hole collisions. [source] Where at a supermassive black hole do gamma-rays come from?ASTRONOMY & GEOPHYSICS, Issue 4 2009Article first published online: 20 JUL 200 Radio observations of galaxy M87 at the time of a massive gamma-ray flare have established that the gamma-ray emission arises close to the central black hole, in the inner jet. [source] Why are AGN found in high-mass galaxies?MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2008Lan Wang ABSTRACT There is a strong observed mass dependence of the fraction of nearby galaxies that contain either low-luminosity [low-ionization nuclear emission-line region (LINER) type] or higher luminosity (Seyfert or composite type) active galactic nuclei (AGN). This implies that either only a small fraction of low-mass galaxies contain black holes, or that the black holes in these systems only accrete rarely or at very low rates, and hence are generally not detectable as AGN. In this paper, we use semi-analytic models implemented in the Millennium Simulation to analyse the mass dependence of the merging histories of dark matter haloes and of the galaxies that reside in them. Only a few per cent of galaxies with stellar masses less than M* < 1010 M, are predicted to have experienced a major merger. The fraction of galaxies that have experienced major mergers increases steeply at larger stellar masses. We argue that if a major merger is required to form the initial seed black hole, the mass dependence of AGN activity in local galaxies can be understood quite naturally. We then investigate when the major mergers that first create these black holes are predicted to occur. High-mass galaxies are predicted to have formed their first black holes at very early epochs. The majority of low-mass galaxies never experience a major merger and hence may not contain a black hole, but a significant fraction of the supermassive black holes that do exist in low-mass galaxies are predicted to have formed recently. [source] Supermassive black hole merger rates: uncertainties from halo merger theoryMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2006Adrienne L. Erickcek ABSTRACT The merger of two supermassive black holes is expected to produce a gravitational-wave signal detectable by the Laser Interferometer Space Antenna(LISA). The rate of supermassive-black-hole mergers is intimately connected to the halo merger rate, and the extended Press-Schechter (EPS) formalism is often employed when calculating the rate at which these events will be observed by LISA. This merger theory is flawed and provides two rates for the merging of the same pair of haloes. We show that the two predictions for the LISA supermassive-black-hole-merger event rate from EPS merger theory are nearly equal because mergers between haloes of similar masses dominate the event rate. An alternative merger rate may be obtained by inverting the Smoluchowski coagulation equation to find the merger rate that preserves the Press,Schechter halo abundance, but these rates are only available for power-law power spectra. We compare the LISA event rates derived from the EPS merger formalism to those derived from the merger rates obtained from the coagulation equation and find that the EPS LISA event rates are 30 per cent higher for a power spectrum spectral index that approximates the full , cold dark matter result of the EPS theory. [source] Forming supermassive black holes by accreting dark and baryon matterMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2006Jian Hu ABSTRACT Given a large-scale mixture of self-interacting dark matter (SIDM) particles and baryon matter distributed in the early Universe, we advance here a two-phase accretion scenario for forming supermassive black holes (SMBHs) with masses around ,109 M, at high redshifts z(,6). The first phase is conceived to involve a rapid quasi-spherical and quasi-steady Bondi accretion of mainly SIDM particles embedded with baryon matter on to seed black holes (BHs) created at redshifts z, 30 by the first generation of massive Population III stars; this earlier phase rapidly gives birth to significantly enlarged seed BH masses of during z, 20,15, where ,0 is the cross-section per unit mass of SIDM particles and Cs is the velocity dispersion in the SIDM halo referred to as an effective ,sound speed'. The second phase of BH mass growth is envisaged to proceed primarily via baryon accretion, eventually leading to SMBH masses of MBH, 109 M,; such SMBHs may form either by z, 6 for a sustained accretion at the Eddington limit or later at lower z for sub-Eddington mean accretion rates. In between these two phases, there is a transitional yet sustained diffusively limited accretion of SIDM particles which in an eventual steady state would be much lower than the accretion rates of the two main phases. We intend to account for the reported detections of a few SMBHs at early epochs, e.g. Sloan Digital Sky Survey (SDSS) 1148+5251 and so forth, without necessarily resorting to either super-Eddington baryon accretion or very frequent BH merging processes. Only extremely massive dark SIDM haloes associated with rare peaks of density fluctuations in the early Universe may harbour such early SMBHs or quasars. Observational consequences are discussed. During the final stage of accumulating a SMBH mass, violent feedback in circumnuclear environs of a galactic nucleus leads to the central bulge formation and gives rise to the familiar empirical MBH,,b correlation inferred for nearby normal galaxies with ,b being the stellar velocity dispersion in the galactic bulge; in our scenario, the central SMBH formation precedes that of the galactic bulge. [source] Evidence that powerful radio jets have a profound influence on the evolution of galaxiesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2004Steve Rawlings ABSTRACT The relationships between supermassive black holes and the properties of their associated dark matter haloes imply that outflows from accreting black holes provide a feedback mechanism regulating galaxy formation. Accreting black holes with weak or undetectable radio jets (radio-quiet quasars) outnumber those with powerful jets (radio-loud quasars) by a factor of ,10,100, so powerful-jet outflows are often neglected. However, whenever powerful jets are triggered, there is a dramatic (factor of ,100) step-function increase in the efficiency of feedback. We use a feedback model, together with the measured space density of flat-spectrum radio-loud quasars, to show that a powerful-jet episode probably occurred in every protocluster in the Universe. Before jet triggering, there was time for gravitational collapse to create many (,10,100) surrounding protogalaxies massive enough to host radio-quiet quasars. After triggering, the powerful jet pushes back and heats ionized gas so that it cannot fall on to these protogalaxies and cool. Once neutral/molecular gas reservoirs become exhausted, there is a synchronized shutdown in both star formation and black hole activity throughout the protocluster. These considerations imply that radio-loud quasars have a profound influence on the evolution of all the galaxies seen in clusters today. [source] A unified model for the evolution of galaxies and quasarsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2000Guinevere Kauffmann We incorporate a simple scheme for the growth of supermassive black holes into semi-analytic models that follow the formation and evolution of galaxies in a cold dark matter-dominated Universe. We assume that supermassive black holes are formed and fuelled during major mergers. If two galaxies of comparable mass merge, their central black holes coalesce and a few per cent of the gas in the merger remnant is accreted by the new black hole over a time-scale of a few times 107 yr. With these simple assumptions, our model not only fits many aspects of the observed evolution of galaxies, but also reproduces quantitatively the observed relation between bulge luminosity and black hole mass in nearby galaxies, the strong evolution of the quasar population with redshift, and the relation between the luminosities of nearby quasars and those of their host galaxies. The strong decline in the number density of quasars from z,2 to z=0 is a result of the combination of three effects: (i) a decrease in the merging rate; (ii) a decrease in the amount of cold gas available to fuel black holes, and (iii) an increase in the time-scale for gas accretion. The predicted decline in the total content of cold gas in galaxies is consistent with that inferred from observations of damped Ly, systems. Our results strongly suggest that the evolution of supermassive black holes, quasars and starburst galaxies is inextricably linked to the hierarchical build-up of galaxies. [source] Populations of supersoft X-ray sources: Novae, tidal disruption, Type Ia supernovae, accretion-induced collapse, ionization, and intermediatemass black holes?ASTRONOMISCHE NACHRICHTEN, Issue 2 2010R. Di Stefano Abstract Observations of hundreds of supersoft X-ray sources (SSSs) in external galaxies have shed light on the diversity of the class and on the natures of the sources. SSSs are linked to the physics of Type Ia supernovae and accretion-induced collapse, ultraluminous X-ray sources and black holes, the ionization of the interstellar medium, and tidal disruption by supermassive black holes. The class of SSSs has an extension to higher luminosities: ultraluminous SSSs have luminosities above 1039 erg s,1. There is also an extension to higher energies: quasisoft X-ray sources (QSSs) emit photons with energies above 1 keV, but few or none with energies above 2 keV. Finally, a significant fraction of the SSSs found in external galaxies switch states between observations, becoming either quasisoft or hard. For many systems "supersoft" refers to a temporary state; SSSs are sources, possibly including a variety of fundamentally different system types, that pass through such a state. We review those results derived from extragalactic data and related theoretical work that are most surprising and that suggest directions for future research (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Bright but obscured chemical powerhousesASTRONOMY & GEOPHYSICS, Issue 6 2008Article first published online: 7 APR 200 Ultraluminous infrared galaxies emit immense amounts of energy thanks to their speedy transformation of interstellar gas into young stars, and to their supermassive black holes. But their dense gas and dust clouds have obscured the details , and the products , of this intense star formation, until now. [source] | ||||||||||